Carlos,
there could be so many contributory factors to the dissapearance of your grass.
It looks in the picture like an area that has been covered in leaves for a while. It only takes a week for leaves to cut out all light for it to have this effect.
Another factor could be, is the soil compacted, thus not allowing any water to drain properly. Is the soil very moist/wet. Try aerating the area with a fork, pushing the tines into the soil about 5" and pulling out leaving little holes that would help drainage. If this is the case, then after all frosts have gone, give the area a good aerating using the fork method, sprinkle a little lawn sand around and sow some fresh grass seed.
Without actually seeing it properly it is hard to diagnose the problem thoroughly, but hope this has been of some help.
Feel free to pm me any questions regarding this matter, good luck,
Bryan.